Radioisotopes are fundamental tools in experimental biology. Their use has permitted the development of powerful approaches to the study of metabolic transformation and regulation. One such approach is dual radioisotope labeling in which different molecular events are tracked simultaneously by separate isotopes. Using channel discrimination on a scintillation counter, one can attain quantitative accuracy for two isotopes over a wide range of isotopic ratios. However, scintillation counting analyzes one sample at a time and is therefore difficult to combine with powerful spatial separation techniques such as gel electrophoresis.
Several investigators have attempted to apply dual tracer methods, particularly double radioisotope analysis to two-dimensional autoradiograms using X-ray film as the recording medium (McConkey, Choo, Lecocq, Walton). Unfortunately, accurate quantitation of X-ray film autoradiograms is difficult to achieve since X-ray film has a limited dynamic range (about 200:1), is relatively insensitive to beta-radiation, and exhibits a non-linear response. For these reasons, dual label methods are not widely used with X-ray film images.
U.S. Pat. No. 4,734,581 to M. Hashive describes an autoradiographic process for obtaining information on two dimensional locations of radioactively labeled substances. Japanese Pat. No. 62-93679 to H. Shiraishi describes a double-sided storage phosphor imaging plate that can be used for dual label autoradiographic imaging.
An object of the invention was to devise an improved dual label method for two-dimensional quantitative analysis that uses standard storage phosphor screens.